As I understand it, most power plant investment decisions for recently opened new powerplants were made during the boom days in the lead up to the 2008 crisis. From the turn of the century to the crisis, German electricity production climed more than 10% while prices kept on rising. One can therefore not blame utilities for wanting to build more power plants.
Then of course the party came to an end and now production is down about 3% while the price essentially halved. Had the pre-recession trends continued such as almost all major energy authorities predicted, demand would have climed another 10% up to now instead of declining and the capacity additions by utilities would have made sense.
About the solar PV, no-one is disputing the fact that if FiT and/or residential electricity prices rise high enough rooftop solar becomes profitable for individual households. The issue is just that, on a societal level, the value of solar PV electricity is about €40/MWh in Germany (and set to fall further due to increasing intermittency effects at higher penetration) while the LCOE (under low financing costs that misprice the risks) amount to about €120/MWh.
Putting up a solar array shifts electricity levies (now fully half of the German residential electricity price) and grid capital costs (which cannot be avoided at all by solar PV in Germany) from the homeowner to the rest of the population. This wealth transfer is obviously detrimental to broader society.
I'm also a bit unclear about how a German household will be able to achieve 75% yearly self-consumption from a solar array oversized by just 50%. The seasonal output of PV in Germany is badly misalligned with demand (winter output is an order of magnitude less than summer output) and batteries will have no influence on this. Germany also has many longer cloudy spells where battery storage can only play a very minor role.